A report on Chemical element

The chemical elements ordered in the periodic table

$Estimated distribution of dark matter and dark energy in the universe. Only the fraction of the mass and energy in the universe labeled "atoms" is composed of chemical elements.$

Periodic table showing the cosmogenic origin of each element in the Big Bang, or in large or small stars. Small stars can produce certain elements up to sulfur, by the alpha process. Supernovae are needed to produce "heavy" elements (those beyond iron and nickel) rapidly by neutron buildup, in the r-process. Certain large stars slowly produce other elements heavier than iron, in the s-process; these may then be blown into space in the off-gassing of planetary nebulae

Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, from the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers (the Oddo-Harkins rule), and (2) a general decrease in abundance as elements become heavier. Iron is especially common because it represents the minimum energy nuclide that can be made by fusion of helium in supernovae.

Mendeleev's 1869 periodic table: An experiment on a system of elements. Based on their atomic weights and chemical similarities.

Species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species.

- Chemical element

148 related topics with Alpha

Bromine

11 links

Structure of N-bromosuccinimide, a common brominating reagent in organic chemistry

Bromine addition to alkene reaction mechanism

View of salt evaporation pans on the Dead Sea, where Jordan (right) and Israel (left) produce salt and bromine

Baltimore's Emerson Bromo-Seltzer Tower, originally part of the headquarters of Emerson Drug Company, which made Bromo-Seltzer

2-Octyl 4-bromo-3-oxobutanoate, an organobromine compound found in mammalian cerebrospinal fluid

Bromine is a chemical element with the symbol Br and atomic number 35.

Gallium

11 links

99.9999% (6N) gallium sealed in vacuum ampoule

Galinstan easily wetting a piece of ordinary glass

Owing to their low melting points, gallium and its alloys can be shaped into various 3D forms using 3D printing and additive manufacturing

Gallium is a chemical element with the symbol Ga and atomic number 31.

Astatine

7 links

Structure of astatine monoiodide, one of the astatine interhalogens and the heaviest known diatomic interhalogen.

Emilio Segrè, one of the discoverers of the main-group element astatine

Neptunium series, showing the decay products, including astatine-217, formed from neptunium-237

Astatine is a chemical element with the symbol At and atomic number 85.

Artificial nuclide americium-241 emitting alpha particles inserted into a cloud chamber for visualisation

Radionuclide

9 links

Nuclide that has excess nuclear energy, making it unstable.

Americium-241 container in a smoke detector.

Americium-241 capsule as found in smoke detector. The circle of darker metal in the center is americium-241; the surrounding casing is aluminium.

All chemical elements can exist as radionuclides.

Atomic nucleus

9 links

Small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment.

A figurative depiction of the helium-4 atom with the electron cloud in shades of gray. In the nucleus, the two protons and two neutrons are depicted in red and blue. This depiction shows the particles as separate, whereas in an actual helium atom, the protons are superimposed in space and most likely found at the very center of the nucleus, and the same is true of the two neutrons. Thus, all four particles are most likely found in exactly the same space, at the central point. Classical images of separate particles fail to model known charge distributions in very small nuclei. A more accurate image is that the spatial distribution of nucleons in a helium nucleus is much closer to the helium electron cloud shown here, although on a far smaller scale, than to the fanciful nucleus image. Both the helium atom and its nucleus are spherically symmetric.

Which chemical element an atom represents is determined by the number of protons in the nucleus; the neutral atom will have an equal number of electrons orbiting that nucleus.